An Experimental Study of Mobilization and Creeping Flow of Oil Slugs in a Water-Filled Capillary

Abstract

An experimental investigation was carried out on mobilization and very slow flow of oil slugs in a capillary tube. The pressure drop of the slug flow was measured at every stage of mobilizing and moving the oil slugs as a function of capillary number in the range of 4 × 10 −7 -6 × 10 −6 . The pressure drop across the oil slug experienced three stages: build-up, hold-up, and steady stages. During the build-up stage, the convex rear end of the slug was becoming concave into the oil slug and the convex front end of the slug moved ahead to form a new portion of the slug. At the hold-up stage, both the concave rear end and the front end continued to advance, and the initial contact line of the oil slug with the tube wall through a very thin water film was being shortened. At this stage, the pressure drop reached a maximum value and remained nearly constant. At the steady stage, after the oil slug was completely mobilized out of the original contact region, the differential pressure had a step-drop first, and then the oil slug flowed at a lower differential pressure depending on the flow rate. Numerous slug flow tests of this study showed that the hold-up pressure drop was always higher than the steady stage pressure drop. Results also showed that the measured extra pressure drop was significantly high compared to the pressure drop calculated from Poiseuille equation, which is still commonly used in network modeling of multiphase flow in porous media.

The distribution of fluids in irregular capillary tubes: a new capillary model based on the single-corner capillary

“…When the number of edges goes to infinity, the polygon can be considered circular. Although the film between the nonwetting phase and the inner walls of the tube is extremely thin, the influence of the liquid membrane on two-phase flow is non-negligible, on the condition that the viscosities of the phases are unequal and the scale of the cross section of the tube is very small (Dai et al 2016;Dai and Wang 2014;Dai and Zhang 2013;Dong et al 2009;Fairbrother and Stubbs 1935;Taylor 1961). The influence of the film on the flow in the tubes with polygonal cross sections will be discussed in a later section.…”

Droplet deformation under confined Poiseuille flow

“…In a later study, Schwartz et al [33] investigated the effect of viscosity, which was found to increase the film thickness, without affecting the dependence on Ca. Recently, an experimental investigation of a liquid slug has been reported by Dong et al [34], but no comparison with theoretical predictions has been provided. A possible interpretation of the discrepancy between theory and experiments is the presence of surface-active agents at the bubble or droplet interface.…”

Numerical Study on Mobilization of Oil Slugs in Capillary Model with Level set Approach

“…In the efforts to reveal the mechanism, capillary models have been found to be useful. Experimental investigations on the mobilization of oil slugs in capillary models have been reported (Dong et al, 2009;Zhang and Dai, 2012). Recently, Dai and Zhang (2013) presented their findings of the presence and role of a water film in mobilizing an oil slug in a capillary model and some effects of the water film on the motion of the oil slug.…”